As "E57" mentioned, there have been some threads in the "Electrical Theory and Applications" area, regarding Harmonics. Been discussed in other areas of ECN too.

In a Nutshell, Harmonics are Reflected Currents from certain Equipment connected to an AC source. They are reflected back into the System at multiples of the Fundamental Frequency - such as if the Fundamental Frequency is 60 Hz, the "Orders" are 120 Hz, 180 Hz, 240 Hz, etc.

In Electrical Circuitry/Power, the ODD order Harmonics (such as the 3rd, 5th, 7th, etc.) are the ones that normally become "Zero Sequenced" - and tend to create issues, such as the issues dealing with "Triple-N" Currents flowing on a Common Grounded Conductor of a 4 Wire Wye System.These "Triple-N" Currents are additive levels of the 3rd order Harmonic Frequencies (3rd, 9th, etc.) adding up from loads connected between Phase Lines "A"-"N", "B"-"N", and "C"-"N".

The EVEN Order Harmonics in an AC Power System are either Positive Sequenced, or Negative Sequenced, and tend to be of low effect to the System's performance.

These Harmonics can be dealt with in different ways: Filters, Circuitry, "K" Rating of Transformers, Equipment Design, and such.

On the flip side of the coin, there are Harmonics in Audio (Sound), which attribute to the complete percieved "Voice" heard.(there are others which contribute - such as "Envelope", Attack", "Fundamental(s)", "Delay/Decay", and such).

Harmonics in normal Audible propagnation (typically sound transmitted through the surrunding air), will have the EVEN Orders of the Fundamental(s) causing the most effects - or in the idea of AC Power Systems, they are "Zero-Sequenced"; whereas the ODD Orders will have less effects.They are opposite of AC Power Systems.

BTW, the Harmonic Distortion of an Acoustical Waveform puts the "Fuzz" sound into an Electric Guitar's distortion sound output.

Just some mini bits of information to ponder!Hope it's enlightening (sp???).

Feel free to respond and for others to continue this discussion - or best (maybe) to take this to the "Electrical Theory and Applications" area.

A long long time ago, far away in another galaxy, I remenber as an apprentice building an amplifier with our Apprentice Master, Mr. James Plaster (ex Sgt. REME) of sacred memory, whom I truly feared. He was a fierce, red faced man, much given to explosions of anger: "Drilled a bleedin' hole through your hand, boy? You won't be doing that again in a hurry!". He departed this life over 45 years ago. We had trouble with harmonics of unknown origin creating noise, which spoiled the performance. The Master said we could filter out the harmonics and we built a device with a shunt coil in series ( ? I think?) with some condensers. If I remember it right, this had to be 'tuned' so as the impedance of the unit was zero at the ripple frequency of the harmonic, and this would 'short out' the high frequency volts. I think we put it across the supply. Mr. P worked out the number of turns with log tables. I only remember the incident because some cretin electrocuted me with with one of the 500v paper condensers wired to my locker as a 'joke'. I literally 'flew' across the shop like Peter Pan. The amp used thermionic-valves of course, none of them useless, new-fangled transistors for Mr.P! The harmonic was measured by the electronics guy at, I'm sure it was, 6 times 50hz = 300hz and there were others far higher than that but faint. Anyway, I moved on to the machine shop soon after, and Mr. P threw one too many wobblies and 'popped his clogs' with a H.A. I'd forgotten it all until the 'harmonic' post appeared. Feel free to shoot me down if I remembered it all wrong.

Scott, thanks for the info. I did a search for this and didn't find any real answers on the "Theory and Applications" thread so I thought I would post something here to try to get some input. "mostly because I thought harmonics wasn't an application also".

However, I don't think I can move this, maybe Bill can then.

I'll try to start one there, but the guitar thing and the voice thing will confuse farther.

Can we stick to power for the discussion first, as so I can understand that, and then move to the accustical side.

A lot of utility companies who are facing harmonics issues generated by customers are taking a new approach.

They install protective relays that measure the harmonics and have penalties in their service contracts. I've heard of some that disconnect a customer who is contirbuting high levels of harmonics, and others that charge them fines whent hey cross certain thresholds.

Devices that can measure this are now quite inexpensive, and it seems a reasonable way to go.